Explanation of NMR experiments on doped cuprates using the frustration model

We investigate a phenomenological model for the spin glass phase of La_{2-x}Sr_xCuO_4, in which it is assumed that holes doped into the CuO_2 planes localize near their Sr dopant, where they cause a dipolar frustration of the antiferromagnetic environment. In absence of long-range antiferromagnetic order, the spin system can reduce frustration, and also its free energy, by forming a state with an ordered orientation of the dipole moments, which leads to the appearance of spiral spin correlations. To investigate this model, a non-linear sigma model is used in which disorder is introduced via a randomly fluctuating gauge field. A renormalization group study shows that the collinear fixed point of the model is destroyed through the disorder and that the disorder coupling leads to an additive renormalization of the order parameter stiffness. Further, the stability of the spiral state against the formation of topological defects is investigated with the use of the replica trick. A critical disorder strength is found beyond which topological defects proliferate. Comparing our results with experimental data, it is found that for a hole density x > 0.02, i.e. in the entire spin glass regime, the disorder strength exceeds the critical threshold. In addition, some experiments are proposed in order to distinguish if the incommensurabilities observed in neutron scattering experiments correspond to a diagonal stripe or a spiral phase.Comment: 22 pages, 11 figures, revised version, short discussion on Li doped samples added to Sec.IV. To appear in PRB 01 January 200

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“…We mention further that the linear scaling of the width of the distribution of local staggered moments is also consistent with a dipole model. 27…”

Section: A Ferromagnetic Bonds As An Example Of Dipolar Frustrationmentioning

confidence: 99%

Spin-glass phase of cuprates

2004

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“…The frustration model also predicted a magnetic spin glass phase for x > x c [7], as recently confirmed in detail in doped LCO and YBCO [3,[11][12][13]. Furthermore, the model successfully reproduced the local field distributions observed in NQR experiments [14]. In earlier work, Glazman and Ioselevich [15] analyzed the planar non-linear σ model with random dipolar impurities, assuming that the dipole moments are annealed and expanding in x/T .…”

mentioning

confidence: 90%

“…At low concentrations, z < 0.10, this is in good agreement with the 1/S expansion result, [18] ρ s (z)/ρ s (0) = 1 − 3.14z, if one uses the approximation B(z) ≈ B(0) in Eq. (14). At higher concentrations the ratio ρ s (z)/ρ s (0) in the classical limit decreases with dilution approximately as ρ s (z)/ρ s (0) = 1 − 3.14z + 1.57z 2 , [18] i.e.…”

mentioning

confidence: 99%

Competing frustration and dilution effects on the antiferromagnetism inLa2−xSrx
Korenblit
¹
,
Aharony
²
,
Entin‐Wohlman
³

1999
Phys. Rev. B
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13
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11
0
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The combined effects of hole doping and magnetic dilution on a lamellar Heisenberg antiferromagnet are studied in the framework of the frustration model. Magnetic vacancies are argued to remove some of the frustrating bonds generated by the holes, thus explaining the increase in the temperature and concentration ranges exhibiting three dimensional long range order. The dependence of the Néel temperature on both hole and vacancy concentrations is derived quantitatively from earlier renormalization group calculations for the non-dilute case, and the results reproduce experimental data with no new adjustable parameters. 74.72Dn, 75.30.Kz, 75.50.Ee Since the discovery of high-T c superconductors much effort was invested in the investigation of the effect of dopants on the magnetic properties of the parent compounds La 2 CuO 4 (LCO) and YBa 2 Cu 3 O 6 (YBCO). It is now well established that even a very small dopant concentration, which introduces a concentration x of holes into the CuO 2 planes, strongly reduces the Néel temperature, T N . In LCO, doped with strontium or with excess oxygen, the antiferromagnetic long range order (AFLRO) disappears at a hole concentration x c ≈ 2% [1], while in YBCO x c ≈ 3.5% [2,3]. In contrast, the effect of Cu dilution by nonmagnetic Zn is much weaker. Like in percolation, the AFLRO persists at Zn concentration, z, as large as 25 % [4].Recently, Hücker and coworkers [4] studied the phase diagram of La 2−x Sr x Cu 1−z Zn z O 4 , and found surprising results: It appears that the vacancies introduced by Zn doping weaken the destructive effect of holes (introduced by the Sr) on the AFLRO. E. g., in a sample with z = 15%, the critical concentration x c of the holes is approximately 3%, i.e. larger than in vacancy free LCO. Also, at x = 0.017 the Néel temperature has a maximum as function of z, implying a reentrant transition! To explain these phenomena, Hücker et al. measured the variable range hopping conductivity in their samples (at temperatures lower than 150 K all samples were insulators), and showed that Zn doping lowers the localization radius of the holes. Their qualitative conclusion was that as the holes become more "mobile", their influence on T N increases. However, so far there has been no quantitative understanding of the combined dependence of T N on both x and z.In this paper we present a quantitative calculation, which reproduces all the surprising features of the function T N (x, z). Our theory extends an earlier calculation [5], which treated the effects of quenched hole doping on the AFLRO in Sr doped LCO, i. e. calculated T N (x, 0). The same parameters were then used to reproduce the observed T N (x) for the bi-layer Ca doped YBCO [6]. Here we reproduce the full function T N (x, z), with practically no additional adjustable parameters.Our theory is based on the frustration model [7], which argues that when a hole is localized on a Cu-O-Cu bond [8,9], it effectively turns the interaction between the Cu spins strongly ferromagnetic, causing a canting of the surrou...

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“…As we show below, a previous attempt [24] fails, and thus we present improved arguments leading to a valid solution close to and far away from the frustrating bond. Other work has been unable to solve analytically this part of the frustrating bond problem [25] (although it is clear that they are aware of the issues that we have finally solved).…”

Section: Spin Deviations Of a Frustrating Bondmentioning

confidence: 99%

Spin twists, domain walls, and the cluster spin-glass phase of weakly doped cuprates

Beach

Gooding

2000

Eur. Phys. J. B

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We examine the role of spin twists in the formation of domain walls, often called stripes, by focusing on the spin textures found in the cluster spin glass phases of La2−xSrxCuO4 and Y1−xCaxBa2Cu3O6. To this end, we derive improved analytic expressions for the spin distortions produced by a frustrating bond, both near the core region of the bond and in the far field, and then derive an improved expression for interaction energies between such bonds. We critique our analytical theory by comparison to numerical solutions of this problem and find excellent agreement. By looking at collections of small numbers of such bonds localized in some region of a lattice, we demonstrate the stability of small "clusters" of spins, each cluster having its own orientation of its antiferromagnetic order parameter. Then, we display a domain wall corresponding to spin twists between clusters of locally ordered spins showing how spin twists can serve as a mechanism for stripe formation. Since the charges are localized in this model, we emphasize that these domain walls are produced in a situation for which no kinetic energy is present in the problem. PACS. 75.50.Lk Spin glasses and other random magnets -74.72.-h High-Tc compounds

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Explanation of NMR experiments on doped cuprates using the frustration model

Cited by 3 publications

References 36 publications

Spin-glass phase of cuprates

Spin-glass phase of cuprates

Competing frustration and dilution effects on the antiferromagnetism inLa2−xSrx
Korenblit
¹
,
Aharony
²
,
Entin‐Wohlman
³

1999
Phys. Rev. B
Self Cite
13
0
11
0
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Spin twists, domain walls, and the cluster spin-glass phase of weakly doped cuprates

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Explanation of NMR experiments on doped cuprates using the frustration model

Cited by 3 publications

References 36 publications

Spin-glass phase of cuprates

Spin-glass phase of cuprates

Competing frustration and dilution effects on the antiferromagnetism inLa2−xSrxKorenblit1, Aharony2, Entin‐Wohlman3 1999Phys. Rev. BSelf Cite130110View full textAdd to dashboardCite

Spin twists, domain walls, and the cluster spin-glass phase of weakly doped cuprates

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Competing frustration and dilution effects on the antiferromagnetism inLa2−xSrx
Korenblit
¹
,
Aharony
²
,
Entin‐Wohlman
³

1999
Phys. Rev. B
Self Cite
13
0
11
0
View full text Add to dashboard Cite